AP Annual Conference: Results from AP Physics Exams

Results from AP Exams

Jiang Yu, Chief Reader

I attended this session to gain some insights into how the AP Physics B exam is scored and what common mistakes students made on the exam.

  • Question B1
    • 6.6/10
    • common errors
      • omit one of the three forces or add a normal force on FBD
      • use unconventional labels for their forces
      • units! students often omitted units
      • not recognize buoyancy is measured in Newtons
      • forces that appeared on the FBD often did not match the ones appeared in subsequent calculations
      • not using physics but general language in justification
  • Question B2
    • 6.0/15
    • common errors
      • applied kinematic equations for constantly accelerated motion to a motion of changing acceleration
      • not recognize that W=Fd can only be used when F is constant
      • not knowing that spring force is not a constant force
      • explanations are not concise and clear
  • Question B3
    • 3.6/10
    • common errors
      • non-linear scaling of axes in graphing
      • best-fit line often is drawn by just connecting points
      • not showing work for calculating slope of the best-fit line
      • not understanding that the light must pass from a higher index of refraction to a lower index of refraction in order to have total internal reflection
  • Question B4
    • 3.6/10
    • common errors
      • not reading the question carefully and not answering what is asked
      • not showing enough work beginning with the correct equations and then all the needed steps leading to an answer
      • messing up the horizontal and the vertical dimensions in calculations
      • deficiency in understanding the conservation of momentum
      • using “energy,” “force,” “momentum” and “velocity” interchangeable in explanations
  • Question B5
    • 3.6/10
    • common errors
      • misunderstanding of the sign conventions in evolved for heat, work and energy
      • not clear with their justifications, but often simply restated the question, and answer without providing further support
      • connected heat or average kinetic energy to temperature, but not to the internal energy
      • used W = -PΔV and did not discuss the effect of temperature on the pressure
  • Question 6
    • 3.5/15
    • common errors
      • simple calculations errors were everywhere
      • incorrect use or value of the magnetic permeability, μo, in Ampere’s Law
      • not understanding the intent of parts (a) & (b)
      • did not clearly understand the nature of the question and the connection of the parts to each other
  • Question 7
    • 2.7/10
    • common errors
      • the most common errors were the result of a lack of understanding of atomic states and associated energy levels. Students seemed to choose and use the equations without basic understanding of the physics involved.

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